node. Currently this is rewritten to a disk_image tag in the
emulab-ops project of the CM the node is allocated from. This works
nicely for STD images since all Emulabs tend to have the same STD
images, but will not work for localized images. All of this image
stuff in cooked mode needs a bunch of work.

Also add support for talking to non elvin-compat nodes on other CMs by
having the event clients contact another pubsubd instance on the home
boss, which will gateway the events back and forth, munging them as
needed.